In theory, that's how pool mining works over the long term. Small pools will generate fewer blocks, but you'll get a larger share of the block rewards, and over the long term it all evens out. The only reason to go with a larger hash pool is more frequent payouts. Using a large hash rate pool might be a good way to go if you are mining a coin that you just want some quick results from... but if you are mining a coin for a while, then you should earn the same amount even on a smaller hash rate pool. There will be some variance due to luck, but again, over the long term it should even out.
That's the theory, alright; the reality seems to be far less rosy if the pool uses PPLNS, however, and these days most of them do (or the equally perverse variant, Pay Per Last N Time, PPLNT).
It's probably well known among those in this thread that as pool hashrate declines the average time to find each block goes up; perhaps less well-known or appreciated is that there will be wilder swings in time to find as pool hashrate goes down as well, because finding a block is a statistical event, not a mathematical certainty. Since PPLNS only pays you for the last n shares submitted (or n time for PPLNT), it automatically assumes an average number of shares (or time) to find each block. The pool operators can specify how much variance in time to find is permissible (ie - the number of standard deviations), but even if they are feeling particularly generous there will be an amount of time (or # of shares) beyond which you get no credit for your work.
The most egregious example of this in my recent experience (though I have collected many equally egregious ones in the short 6 months I've been mining) happened when a previously popular ZEN pool (Zhash.pro) went down for a day or two to change servers and never seemed to get back to its former hashrate, but it was clear to me that the PPLNS parameters still assumed the former hashrate because I was consistently earning around 60-70% of what I should have every 24 hour period. After watching this occur for over a week I finally called the pool operators out on it in their ANN thread and to their credit, they said they would look into it. The next day they reported that they had made some changes to various settings on the pool and lo-n-behold, earnings did improve spectacularly. In fact, for next couple of days I actually earned more than the calculator on minethecoin predicted!
Of course, that party didn't last too long and once again the pool resumed underpaying on a daily basis, except it was closer to 40% of expected, rather than the 60-70% of before. In fact, during my last mining session with them - where I was merely trying to get my existing balance of 0.0475 up to the payout threshold of 0.1 ZEN - I mined for 8 hours at a very consistent 1750 H/s and only earned 0.024 ZEN, rather than the 0.0592 expected. In fact, it took another 8 hours of mining to finally hit 0.1 ZEN, and there was one episode where I mined for 3 hours and only got credit for 0.0011 ZEN the next day because a single block had been found in that 24 hour period (despite the pool claiming its average luck was 0.07 days [ie - 14 blocks per day]).
Consequently, I am now mining ZEN on Suprnova where I am also consistently underpaid, but only by 10%; an amount I can live with, relatively speaking.
really is an amazing tool for 1080ti owners 
))